CFD-Driven Optimization of Diesel Injection for a Hydrogen-Diesel Dual Fuel Engine

Among the alternatives to the use of fossil diesel fuel, dual fuel combustion, leveraging hydrogen as the low-reactivity fuel, represents a promising approach for both reducing pollutant emissions and improving brake thermal efficiency. In addition, this innovative combustion mode requires minimal modifications to the existing Diesel engines architecture. This study is conducted on a Diesel engine (naturally aspirated, 3 cylinder, 1 Liter, direct injection), properly modified by the authors to operate in dual fuel mode with port fuel injection of hydrogen. A set of experimental data is used to calibrate the 1D and the 3D-CFD models for both Diesel and diesel-hydrogen dual fuel configurations. The AVL FIRE M 3D-CFD software is employed to model diesel injection and combustion, while the gas exchange process is analyzed by GT-Power. The validated 3D-CFD model is then leveraged to optimize the baseline diesel injection strategy in dual fuel mode, minimizing diesel consumption while maintaining stable combustion and comparable performance with respect to the baseline Diesel engine. Notably, the analysis highlights that, at low loads—where hydrogen substitution is limited—a diesel injection strategy consisting of two equal fuel pulses is required to ensure stable ignition. However, as the hydrogen fraction increases along with load, a single diesel injection is sufficient to properly ignite the premixed hydrogen-air charge. This approach enables to reduce diesel consumption and engine emissions while maintaining stable combustion.